Induction speed governor



April 14, 1964 J. HELFNER ETAL 3,129,370

INDUCTION SPEED GOVERNOR Filed Dec. 20. 1960 /0 r numv Z I N m 5 5o 52 50 5 I 49 N I Z4 40 M9 H] TI S I I 59 q LSQMIW HTTORNEY United States Patent 3,129,379 INDUCTION SPEED GOVERNOR luies Heltner, Massapeqna, and Paul Fenster, Brooklyn, N.Y., assignors to United Aircraft Corporation, East Hat-third, Conn, a corporation of Delaware Filed Dec. 24B, 196%, Ser. No. 77,089 6 Claims. (Q11. 318-343) Our invention relates to an induction speed governor and more particularly to an improved speed governor which is more reliable and which is more easily adjusted than are speed governors of the prior art.

There are known in the prior art governors for regulating the speed of electric motors. One type of governor consists essentially of a centrifugal switch connected in the motor supply line which opens and inserts a resistance in the line when certain speeds are attained. The speed at which the switch opens is determined by the governor setting. While the governor is operating, the current to the motor is continuously established and is partially interrupted by the centrifugal switch.

Governors of the type described above embody a number of disadvantages. First, since they embody vibrating contacts, problems of arcing and contact point burn out exist. Thus the life of the governor is limited by the life of the contact points. Secondly, the unit is not as reliable as is desired, since the contacts become dirty and, in an extreme case, they may fuse. A further disadvantage of governors of this type is that the motor must be stopped to permit the setting of the governor to be changed. Moreover, a change in the setting aifects the dynamic balance of the rotor.

We have invented an induction speed governor which overcomes the disadvantages of governors of the prior art pointed out hereinabove. The setting of our governor may be changed without stopping the motor and without aifecting the dynamic balance of the rotor. Our improved governor has no vibrating contacts so that problems of arcing and contact point burn out are eliminated. Thus, our governor is more reliable than are governors of the prior art.

One object of our invention is to provide an induction speed governor the setting of which may be changed without stopping the motor which it controls.

A further object of our invention is to provide an induction speed governor which has no vibrating contacts.

A still further object of our invention is to provide an induction speed governor which is more reliable than are governors of the prior art.

Other and further objects of our invention will appear from the following description.

In general, our invention contemplates the provision of an induction speed governor in which a magnet driven by the motor to be controlled vibrates a reed at a frequency somewhat less than the natural frequency of vibration of the reed. In response to reed vibration, there is produced an electrical effect which increases with the amplitude of Vibration to control motor speed. In one form of our invention we feed a voltage generated in response to vibration in the reed to the armature of a direct current motor to oppose the armature voltage. In another form of our invention in response to changes in reed vibration the inductance of an inductor in the circuit of an alternating current motor varies.

In the accompanying drawings which form part of the necessary specification and which are to be read in conjunction therewith and in which like reference characters are used to indicate like parts in the various views:

FIGURE 1 is a schematic view of one form of our induction speed governor used to control the speed of a direct current motor.

FIGURE 2 is a schematic view of another form of our induction speed governor used to control the speed of an alternating current motor.

FIGURE 3 is a curve illustrating the response of the reed of our induction speed governor.

Referring now to FIGURE 1 of the drawings, a direct curent motor indicated generally by the reference character lltl has an armature 12 adapted to be supplied with energy by brushes 14 and 16 in engagement with a commuta-tor lid. The field for the motor 10 may be provided by a permanent magnet having a north pole 22 and a south pole 24. When armature 12 is energized, shaft 26 rotates in a manner known to the art.

We mount a permanent magnet 28 on shaft 26 for rotation therewith. Magnet 28 is an elongated bar magnet having a north pole at one end thereof and a south pole at the other end. We mount a reed 30 formed from a suitable resilient material in a supporting bracket 32 in which the reed St is secured by a screw 34. Bracket 32 may be adjustably positioned on a suitable stationary support 35 by means of a set screw 38 or the like.

We secure a small permanent magnet 40 to the reed Sil for movement therewith. As the bar magnet 28 rotates it alternately attracts and repels the magnet 40 thus to impart a vibration to the reed 30. It will be appreciated from the description of the second form of our invention given hereinafter that we could alternately make the reed 3d of a magnetic material in which case the rotation of the permanent magnet 28 would cause the reed to vibrate. We dispose the magnet 40 in a position at which upon vibration of reed 3% it moves into and out of a winding 42 to induce a voltage in the wind ing. We connect a rectifier i4 and a resistor 46 in series across the coil 42 so that a direct current potential of the polarity indicated exists across resistor 46. We connect the terminals of the resistor 46 respectively to brush 14 and to the positive terminal 48 of a source of direct current potential the negative terminal of which is connected to brush 16.

Referring now to FIGURE 3, we have shown the response curve of the reed Elli as a plot of the amplitude of the vibration as a function of the frequency to which the reed vibrates. As can be seen by reference to the curve, when the reed is driven at its natural frequenc then the amplitude of the vibration is extremely large. We so construct and support the reed 369 as to have a natural frequency of vibration which is somewhat greater than the frequency at which the motor drives the reed when the motor is operating at its desired speed. Thus if the motor tends to speed up, the amplitude of vibration of the reed 3d will increase as well as its frequency of vibration with the result that magnet id enters further into coil 42 and the voltage of resistor 46 increases. It will be seen that this voltage opposes the motor armature voltage so that as the voltage on resistor 46 increases then the motor slows down.

Referring now to FIGURE 2, we have illustrated another form of our invention in which reed 39 is fixed in a stationary support 52. The motor to be controlled in this case may be an alternating current servomotor 54 adapted when energized to drive its shaft 56 carrying the magnet 33. In this form of our invention we mount a slug of magnetic material on the reed 3d so that when magnet 23 rotates it vibrates the reed 30. We could, of course, form the reed 36 itself of magnetic material. We connect a pair of induction coils 6d and 62 in series with motor 54 across a source as of alternating current. The end of the reed. 3t} remote from the support 52 carries for movement therewith a pair of slugs 66 and 68 of magnetic material. When, as magnet 28 rotates, reed 30 vibrates slugs 66 and 68 alternately move into and out of the respective windings 6t and 6.2 thus to vary the inductance in circuit. We so construct the assembly of speed.

the reed 30 and the slugs 66 and 68 as to have a natural frequency of vibration somewhat greater than the frequency of vibration when motor 54 is operating at the desired speed. Thus as the motor speed increases the amplitude of motion of the reed 30 increases and a greater change in inductance in the circuit is produced. Consequently, the current in the motor 54 drops and its speed decreases. It. will be understood of course that the reed 3t? in the form of our invention shown in FIGURE 2 may be adjusted in length. A screw 59 may be actuated to vary the center of gravity of the reed.

In operation of the form of our invention shown in FIGURE 1 when motor It) is energized it drives shaft 26-to rotate magnet 28 to cause reed 38 to vibrate. When the motor is operating at the desired speed, the potential across resistor 46 causes the armature potential to be that potential required to keep the motor rotating at its desired If. for any reason the motor speeds up the amplitude of motion of reed 3ti changes to increase the potential across resistor 46 to decrease the armature potential to cause the motor to slow down. Consequently, if the motor speed drops below the desired speed, the potential across resistor 46 drops and the motor speeds up. The setting of the governor may readily be changed by changing the effective length of reed 343. This can be accomplished by moving bracket 32 along the length of the reed and by repositioning the bracket properly to locate magnet 40.

In operation of the form of our invention shown in FIGURE 2 when motor 54 is energized, shaft 56 rotates to cause magnet 28 to vibrate reed 34 As the reed vibrates, slugs 66 and 68 move into and out of windings 60 and 62 to present a certain effective inductance to the circuit. If the motor is rotating at a great speed, then the inductance is such as will keep the motor rotating at this speed. As, however, the speed of the motor changes, the effective inductance changes in a direction to cause the motor to return to the desired speed.

It will be seen that We have accomplished the objects of our invention. We have provided an induction speed governor which does not require vibrating electric contacts. Our governor is more reliable than are governors of prior art. We may change the setting of our governor Without affecting the dynamic balance of the motor assembly. This setting may be changed without stopping the motor.

It will be understood that certain features and subcom- A is further obvious that various changes may be made in details within the scope of our claims without departing from the spirit of our invention. It is, therefore to be understood that our invention is not to be limited to the specfiic details shown and described.

Having thus described our invention, What we claim is:

1. An induction speed governor for a motor having a shaft and having an input circuit for applying a voltage to said motor including in combination an element having a natural frequency of vibration, means responsive to rotation of-said shaft for vibrating said element at a frequency inthe region of said natural frequency, means responsive to vibration of said member for generating a voltage and means for applying said generated voltage to said motor in a sense to oppose said input voltage.

2. An induction speed governor for a motor having a shaft and having an input circuit for applying a potential to said motor including in combination a vibratory element, means for supporting said element for vibratory movement at its natural frequency of vibration, means responsive to rotation of said shaft for vibrating said element at 'a frequency below its natural frequency of vibration, a coil, a permanent magnet, means mounting one of said coil and magnet on said element to induce a voltage in said coil in response to vibration of said element and means responsive to said voltage for controlling the speed of said motor.

3. An induction speed governor for a motor having a shaft including in combination an element adapted to vibrate at a natural frequency, means responsive to rotation of said shaft for vibrating said element at a frequency in the region of said natural frequency, a source of supply voltage for said motor, a circuit comprising a coil for connecting said source to said motor and a magnetic member carried by said element for movement with respect to said coil in response to vibration of said element for varying the voltage supplied from said source to said motor whereby to control the speed of said motor.

' 4. An induction speed governor for a motor having a shaft including in combination an element adapted to vibrate at a natural frequency, means responsive to rotation of said shaft for vibrating said element at a frequency in the region of and below said natural frequency, a source of supply voltage for said motor, a circuit comprising a coil forconnecting said source to said motor and a magnetic member carried by said element for movement with respect to said'coil in response to vibration of said element for'varying the voltage supplied from said source to said motor whereby to control the speed of said motor.

5. An induction speed governor for a motor having a shaft including in combination an element adapted to vibrate at a natural frequency, means responsive to rotation of said shaft for vibrating said element at a frequency in the region of said natural frequency, a source of supply voltage for said motor, a circuit comprising a coil for connecting said source to said motor, a magnetic member carried by said element for movement with respect to said coil in response to vibration of said element for varying the voltage supplied 7 from said source to said motor whereby to control the speed of said motor, and means for adjusting the natural frequency of vibration of said member.

6. An induction speed governor for a motor having a shaft including in combination an element adapted to vibrate at a natural frequency, magnetic material carried by said'element, a magnet carried by said shaft, means mounting said element for vibratory movement adjacent said magnet whereby said element vibrates in the region of its natural frequency in response to rotation of the shaft, a source of supply voltage for said motor, a circuit comprising a coil for connecting said source to said motor and a magnetic member carried by said element for movement with respect to said coil in response to vibration of said element for varying the voltage supplied from said source to said motor whereby to control the speed of said motor.

Taylor May 22, 1917 Fitzgerald et al May 9, 1933 

1. AN INDUCTION SPEED GOVERNOR FOR A MOTOR HAVING A SHAFT AND HAVING AN INPUT CIRCUIT FOR APPLYING A VOLTAGE TO SAID MOTOR INCLUDING IN COMBINATION AN ELEMENT HAVING A NATURAL FREQUENCY OF VIBRATION, MEANS RESPONSIVE TO ROTATION OF SAID SHAFT FOR VIBRATING SAID ELEMENT AT A FREQUENCY IN THE REGION OF SAID NATURAL FREQUENCY, MEANS RESPONSIVE TO VIBRATION OF SAID MEMBER FOR GENERATING A VOLTAGE AND MEANS FOR APPLYING SAID GENERATED VOLTAGE TO SAID MOTOR IN A SENSE TO OPPOSE SAID INPUT VOLTAGE. 